1. Field of the Invention
This invention pertains to transporting particulate coal through a pipeline as a coal-oil slurry, and particularly to coal-oil slurry pipelines in which crude oil is the slurrying liquid and a useful degree of coal liquefaction occurs during its passage through the pipeline at the existing elevated temperature and pressure conditions.
2. Description of Prior Art
It is apparent that coal will become increasingly prominent as a source of fossil fuel energy in the United States in the future, and thus the volume of coal to be transported from mining regions to points of usage will also be increased. The advantages and technology for transporting coal through pipelines as coal-water slurries are well known, and several patents have issued pertaining to such pipelines. However, in many regions where abundant coal exists, particularly in the western United States, water is not in abundant supply and therefore is not usually available for use in coal transportation via coal-water slurry pipelines. Also, even if water supply is plentiful in the same general area as coal supplies, the water used becomes contaminated during pipeline transportation by impurities in the coal, such as sulfur and iron, resulting in a water treatment or reclamation problem at the termination of the coal-water transportation pipeline.
To overcome these disadvantages of coal-water slurry pipelines for transporting coal, the present inventors have proposed using a coal-oil slurry wherein oil is the slurrying liquid for the coal. Specifically, the major deposits of coal which exist in the western part of the United States suggest that increasingly more of this coal will be moving from west to east. This condition, when coupled with the potential of more Alaskan crude oil or oil products also moving from west coast ports to markets in the mid-west area and passing near abundant coal reserves, makes a coal-oil slurry pipeline feasible and economically attractive. Thus as an example, the same pipeline could be used for transporting both Alaskan crude oil traveling eastward to refineries and western coals to the mid-western markets, and useful hydrocarbon reactions accomplished during transit of such coal-oil slurries through the pipeline.
The general use of coal-oil pipelines for transporting coal have been previously proposed, as disclosed in U.S. Pat. No. 2,128,913 to Burk and U.S. Pat. No. 2,610,900 to Cross. Also, U.S. Pat. No. 3,210,168 to Morway discloses use of a stabilized slurry of pulverized coal coated with liquid hydrocarbon fuel and slurried in water for pumping through pipelines. However, none of these patents proposed accomplishing any useful liquefaction and/or hydrogenation reaction of the coal during its transit through a coal-oil slurry pipeline.